The technical field is flow controls. More specifically, the technical field is flow controls for regulating pressure.
Many applications, such as gas chromatography applications, require a constant pressure in a test vessel in order to obtain accurate measurements of the gas in the test vessel. Pressure regulators are commonly used to maintain the pressure in the test vessel at a constant target pressure to ensure accurate measurements.
A typical pressure regulator includes a chamber having a regulated pressure. The regulated chamber is in fluid communication with the test vessel so that the pressure in the test vessel is regulated along with the pressure in the chamber. The pressure regulator also includes a source of pressurized gas and a valve for releasing the pressurized gas into the chamber. The source of pressurized gas is used to raise the pressure in the chamber when the pressure falls below the target pressure.
One type of valve has an o-ring seal that controls the flow of gas from the source to the chamber. The o-ring is normally biased against a valve seat when the chamber is at the target pressure. When the pressure in the chamber falls below the target pressure, the bias against the o-ring is released, and the o-ring separates from the valve seat, allowing the pressurized gas to flow into the chamber.
A disadvantage to this type of valve is that when the o-ring separates from the valve seat, it does not maintain a stable position. Instead, sections of the o-ring may actually oscillate between separation and contact with the valve seat. Oscillation of the o-ring creates disturbances in the flow of pressurized gas, which causes unstable gas flow through the valve and pressure anomalies in the chamber receiving the pressurized gas. Because the test vessel is in fluid communication with the chamber, the pressure within the test vessel fluctuates, which negatively affects measurements taken in the test vessel.
Accordingly, a need exists for a flow control capable of providing stable fluid flow.
According to one embodiment, a flow control includes a support having a passage and a seal surface, a deformable seal that is engageable with the seal surface, and a bias member for exerting a variable bias against the deformable seal. The seal surface includes channels formed in its surface that extend beneath the deformable seal. The bias member can exert a bias sufficient to cause the deformable seal to fill the channels, preventing flow through the channels. When the bias member decreases the bias against the deformable seal, the deformable seal gradually moves out of the channels, allowing fluid flow through the channels, and through the passage in the flow control.
According to the embodiment, the deformable seal does not need to separate from the seal surface to allow fluid flow. Instead, fluid flow initiates through small, controlled flow areas in the channels created when the deformable seal withdraws from the channels. Because the deformable seal does not need to separate from the seal surface in order to allow fluid flow, disturbances are not created in the fluid flow. Therefore, fluid flow is stable through the flow control.
Other aspects and advantages of the invention will be discussed with reference to the figures and to the detailed description of the preferred embodiments.